There is a growing need for introducing power generating facilities that utilize natural energies, that is, distributed electric power sources to consumers of general households and business corporations. Surplus electric powers generated by such distributed electric power sources are fed into the electric power systems of electric power companies as backward power flows via power distribution lines. The electric powers of these backward power flows may be large disturbances for the electric power companies that have to manage the voltages of their electric power systems. Because electric powers generated by the distributed electric power sources are largely dependent on natural energies, the electric powers are susceptible to the influence of weather, so that it becomes difficult for the electric power companies to manage the voltages of their electric power systems. In addition, in recent years, a new usage configuration of batteries of electric vehicles and the like, in which electric powers are charged up at night and are used during periods when the electric powers are needed, has become widely spread. These batteries can be regarded as parts of the distributed electric power sources.
In order to easily manage the electric power systems, a method in which information about electric power systems are three-dimensionally displayed on the screen of a display device is disclosed in Patent Literature 1. According to this method, the magnitude of voltage of each node or the magnitude of deviation from the node voltage reference value of each node is displayed as the height of a cylindrical column that corresponds to the magnitude, and this cylindrical column is disposed in the upward direction or in the downward direction from the node in the three-dimensional space of the electric power system. The tendency of change of the voltage of each node or the tendency of change of the deviation from the node voltage reference value of each node is displayed by changing the diameters of the upper and lower surfaces of the cylindrical column. In addition, the active and reactive power flows of branches, the capacities of facilities, and the like are also three-dimensionally displayed using solids. Further, when two arbitrary nodes are selected, the sinusoidal waveform with a voltage phase angle is displayed.
On the other hand, Patent Literature 2 disclosed an integral monitoring/controlling system in which the generated power output of each distributed electric power source and the loads of consumer facilities in a smart grid or in a microgrid is monitored and controlled. This system is equipped with an emergency accommodating procedure-creating means for creating accommodating procedures according to which the total sum of generated power outputs of individual distributed electric power sources is matched with the total sum of loads of individual consumer facilities using information obtained by a measurement value-monitoring means and information managed by a consumer information management means in the case where a failure occurs in the corresponding microgrid system or smart grid system.
In addition, Patent Literature 3 discloses a power-distribution-system power-flow simulation device in which individual power consumption values and backward power flows of a lot of consumers can be taken into consideration. According to the device disclosed by Patent Literature 3, plural consumer-load simulation units and distributed electric power source simulation units are provided, and the variations of load powers and the variations of generated powers of the distributed electric power sources such as photovoltaic generation powers at plural consumers such as general households are individually simulated, which makes it possible to calculate the power flows of power distribution systems that are nearer to practical power distribution systems by taking the simulation result into consideration.